WEST, Texas (AP) â€” Families of the 15 people killed in a massive explosion at a Texas fertilizer plant have spent the year since the blast navigating the difficult balance between moving forward and digging for answers from the past.

Many of them filed lawsuits seeking answers after a fire at West Fertilizer Company caused a blast so powerful that it leveled nearby schools and homes, left a wide crater at the plant site, and scattered debris miles away. Key questions about the April 17, 2013, blast remain unanswered, including what sparked the fire and what firefighters knew about the chemicals inside the plant.

The lawsuits against the plant's owners and companies doing business with the plant are mired in a legal process that could eventually uncover new details through testimony and documents. But that process will take at least another year to complete.

Several relatives acknowledged those questions, but said they wanted to move on and not dwell on the past, even as the city itself shows physical signs of progress. About 70 homes have been finished or in the process of construction and the wreckage at West Fertilizer has been long cleared away.

"In some ways, I want to know, 'Why did this happen?'" said Holly Harris, whose husband, Dallas Fire-Rescue Capt. Kenneth Luckey Harris, was killed while trying to pull other firefighters away from the smoldering plant. She is among those who have filed a lawsuit. "But maybe we'll never know, and if we keep trying to figure it out, we'll drive ourselves crazy."

Investigators determined that a fire ignited as many as 34 tons of ammonium nitrate, a common but potentially explosive component in fertilizer that was also used in the 1995 Oklahoma City bombing. But they have not pinpointed what started the fire or announced whether volunteer firefighters rushing into the blaze knew enough about the dangers they faced. Among those killed in West were a dozen volunteer firefighters and others trying to help.

The state fire marshal's office says it will release a report on first responders' deaths later this month. The U.S. Chemical Safety Board is also expected to announce its preliminary findings this month.

But the best chance for the public to find out what happened may be in civil court.

More than 100 people have filed lawsuits against Adair Grain Co., the plant's operator. The city of West, the local school district and the nursing home also sued, as did insurers for damaged businesses and homes.

Adair Grain had $1 million in liability insurance â€” a drop in the bucket toward the hundreds of millions of dollars needed to rebuild schools, homes and infrastructure.

Lawyers expanded their lawsuits to include the companies believed to have supplied ammonium nitrate to the plant, saying those suppliers could have sold a less dangerous fertilizer and ensured customers knew how to store it. One supplier, Illinois-based CF Industries, told federal regulators it had "strong legal and factual defenses to the claims and intend to defend ourselves vigorously."

The first trial is set to begin in January.

Steve Harrison, an attorney involved in the lawsuits, said witness testimony, documents and other evidence the cases uncover could help determine what started the fire and what could have been done to prevent it.

"We're going to examine how the products were manufactured, were they manufactured to the specifications they should have been, and if they weren't, did that make the product unreasonably dangerous," Harrison said. "The question is, 'Who's responsible?'"

But in West, a central Texas town of 2,800 people, several residents told The Associated Press in interviews that they were trying not to blame anyone.

"To me, I don't really care what happened," said Brian Uptmor, whose brother Buck was killed while trying to move animals away from the facility. "It was an accident. That's all it was. It was an accident. Being upset at everyone involved it not going to bring anyone back."

Uptmor said he's proud of his town's recovery: People whose homes were destroyed are moving into new ones and rodeo events at Westfest, the annual Czech festival celebrating the town's century-old heritage, resumed last summer. A new nursing home is under construction, with a new high school and middle school soon to follow.

West's mayor, Tommy Muska, said the city was obligated to file a lawsuit to pay for rebuilding, but he's more concerned with leading his town to move forward.

"If you look back, you trip and fall," Muska said.

Harris also hopes to move forward. She credits her faith and family for helping her through the last year, noting that a second of her three sons has since decided to become a Dallas firefighter.

"I hold faith in God that he's got control of this," Harris said. "I don't understand why this happened or how it could have been prevented or anything, but I've just got to accept it."